

The idea of the crouch is not really to be shorter than surrounding structures (maybe that is a minor aspect), but rather to reduce the step voltage (the voltage between your two feet). If you have only one point where you touch the ground, as you do when your feet are very close together, the risk of deadly currents passing through your body is minimised. This will of course not help you when the lightning strikes you directly, but that is not the most common case anyway. People usually die from the large current passing by their heart when they stand next to a lightning strike, and there is a distribution of electric potential across the ground. This is not a myth and not debunked. It’s just a matter of priorities. If there is safety nearby, you should obviously seek it out. If not, however, then to crouch is the best thing you can do.
That’s the very reason why it is indeed helpful to crouch when there is no safety nearby. Putting your feet close together reduces the step voltage (the voltage across your feet), making it less likely that a deadly current flows through your heart when there are strong potentials on the ground.